Raman spectroscopy is an effective tool for identifying and characterizing a vast array of substances. In Raman spectroscopy, light typically from a laser and of a known wavelength (typically infrared or near infrared) is directed at a specimen. The laser light (also sometimes referred to as the Raman pump) interacts with the electron clouds in the molecules of the specimen and, as a result of this interaction, experiences selected wavelength shifting. The precise nature of this wavelength shifting depends upon the materials present in the specimen. A unique wavelength signature (typically called the Raman signature) is produced by each specimen. This unique Raman signature permits the specimen to be identified and characterized. More specifically, the spectrum of light returning from the specimen is analyzed with a spectrometer so as to identify the Raman-induced wavelength shifting in the Raman pump light, and then this wavelength signature is compared (e.g., by a computer) with a library of known Raman signatures, whereby to identify the precise nature of the specimen. Raman spectroscopy is widely used in scientific, commercial and public safety areas. Recent technological advances have made it possible to significantly reduce the size and cost of Raman spectroscopy systems. This has in turn increased the range of practical applications for Raman spectroscopy. For example, portable units have recently become available for various field uses, such as the on-site identification of potentially hazardous substances.
The interception of illegal drugs, such as heroin, has become a severe policing problem worldwide. It is difficult for law enforcement personnel in the field to at least initially identify any particular substance as likely being a prohibited one. This can lead to false arrests or releasing suspects who are indeed carrying such illegal drugs. While a properly equipped lab can make a definitive analysis, typical lab equipment does not lend itself to use by law enforcement personnel in the field because it is either too heavy, cumbersome, difficult to operate, or too expensive to distribute widely to large numbers of law enforcement personnel.